Check the appropriate box below
if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below):

☐

Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

Indicate by check mark whether the registrant is an emerging growth company as
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Emerging growth company ☐

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or
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Item 4.01. Changes in Registrants Certifying Accountant.

(a) Dismissal of Independent Registered Public Accounting Firm.

On May 26, 2017, Savara Inc. a Delaware corporation formerly known as Mast Therapeutics, Inc. (the Company) dismissed
Mayer Hoffman McCann P.C. (MHM), which was serving as the Companys independent registered public accounting firm. The decision to change accountants was approved by the audit committee of the Companys board of
directors (the Audit Committee).

The report of MHM on the Companys consolidated financial statements for the
year ended December 31, 2016 did not contain an adverse opinion or disclaimer of opinion, nor was it qualified or modified as to uncertainty, audit scope, or accounting principles, except that the report included an explanatory paragraph
related to the uncertainty of the Companys ability to continue as a going concern.

During the Companys most recent fiscal
year, which ended December 31, 2016, and the subsequent interim period through May 26, 2017 there were no: (1) disagreements (as defined in Item 304(a)(1)(iv) of Regulation S-K and the related
instructions) with MHM on any matter of accounting principles or practices, financial statement disclosure, or auditing scope or procedures, which disagreement if not resolved to the satisfaction of MHM would have caused MHM to make reference
thereto in its reports on the consolidated financial statements for such years, or (2) reportable events (as described in Item 304(a)(1)(v) of Regulation S-K).

The Company delivered a copy of this Current Report on Form 8-K to MHM on May 26, 2017 and
requested that a letter addressed to the SEC stating whether or not it agrees with the statements made in response to this Item 4.01 and, if not, stating the respects in which it does not agree. MHM responded with a letter dated May 30, 2017,
stating its agreement with such statements, a copy of which is filed herewith as Exhibit 16.1.

(b) Engagement of New Independent
Registered Public Accounting Firm.

On May 25, 2017, the Audit Committee approved the engagement of PricewaterhouseCoopers LLP as the
Companys independent registered public accounting firm for the fiscal year ending December 31, 2017. Prior to the completion of the Companys business combination with Aravas Inc., a Delaware corporation formerly known as Savara Inc.
(Aravas), PricewaterhouseCoopers LLP served as the auditor of Aravas.

PricewaterhouseCoopers LLP served as the
principal accountants for the Company from June 28, 2011 until March 30, 2016, and PricewaterhouseCoopers LLP audited the Companys financial statements for the years ended December 31, 2015, 2014, 2013, 2012 and 2011. Other than
as required in connection with such audits, during the years ended December 31, 2016 and 2015, and the subsequent interim period through May 25, 2017, neither the Company nor anyone on its behalf consulted with PricewaterhouseCoopers LLP,
regarding either (i) the application of accounting principles to a specific transaction, completed or proposed, or the type of audit opinion that might be rendered on the Companys financial statements, and neither a written report nor
oral advice was provided to the Company that PricewaterhouseCoopers LLP concluded was an important factor considered by the Company in reaching a decision as to any accounting, auditing or financial reporting issue or (ii) any matter that was
either the subject of a disagreement (as defined in Item 304(a)(1)(iv) of Regulation S-K and the related instructions) or a reportable event (as described in Item 304(a)(1)(v) of Regulation S-K).

Item 9.01. Financial Statements and Exhibits.

(d) Exhibits.

Exhibit No.

Description

16.1

Letter from Mayer Hoffman McCann P.C. to the Securities and Exchange Commission, dated May 30, 2017

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by
the undersigned hereunto duly authorized.

Date: May 30, 2017

SAVARA INC.,

a Delaware
corporation

By:

/s/ Dave Lowrance

Dave Lowrance

Chief Financial
Officer

EXHIBIT INDEX

Exhibit

Description

16.1

Letter from Mayer Hoffman McCann P.C. to the Securities and Exchange Commission, dated May 30, 2017

EX-16.1

Exhibit 16.1

May 30, 2017

U.S. Securities and Exchange Commission

100 F Street, NE

Washington, DC 20549

Ladies and Gentlemen:

We were previously
independent accountants for Savara Inc., formerly known as Mast Therapeutics, Inc. (the Company). On May 26, 2017, our appointment as the Companys independent accountants was terminated. We have read the Companys
statements included under Item 4.01 of its Current Report on Form 8-K dated on or about May 30, 2017, and we agree with the statements set forth therein insofar as such comments relate to us.